1. Field of the Invention
The present invention relates to a method for compensating writing power in an optical disc device.
2. Background of the Related Art
Generally, an optical disc device detects optimum writing power through optimum power calibration (OPC), and performs a recording operation based on the detected optimum writing power. An OPC for a recordable optical disc (for example, a DVD-R) is described below.
First, a predetermined amount of test data is recorded in a test area of the optical disc. For example, regarding the recordable optical disc (DVD-R), the test data is recorded in 1ECC block (16 sectors) each time when performing OPCs. Here, as shown in FIG. 1, with reference to writing power (hereafter Pref) corresponding to target β value, βtarget, which is defined or predetermined by the manufacturer of the optical disc, the test data are recorded while writing power is changed on the basis of a predetermined amount (for example, Pref±0.6 mW).
After recording of the test data is completed, the test data are sequentially read out, and a β value is detected from the played RF signal for the readout test. The β value, detected through asymmetry of the played RF signal, is proportional to writing power.
After detection of the β value is completed, on the basis of the relation between each writing power, and the detected β value corresponding to the writing power and the target β value, βtarget, optimum writing power Popt is detected. After that, the detected optimum writing power is used when a writing operation is requested.
However, since temperature variation occurs around the optical pick-up, and each disc has individual disc characteristics such as tilt components, and individual optical characteristics, etc., writing operations cannot be implemented resulting in the best writing quality using only the detected optimum writing power. To compensate optimum writing power, the prior art method controls writing power in real time through ROPC operation (an operation that compensates writing power according to light amount based on the monitoring of a light amount reflected from the disc while performing a writing operation). From test results, however, the ROPC operation can only slightly enhance writing quality.
As described above, the prior art methods and apparatus for compensating writing power in an optical disc have various disadvantages. For example, the prior art method has disadvantages in that additional parts are required, such as a thermistor and an ADC, to compensate writing power according to the temperature variation. Accordingly, the size of the device is enlarged and the cost is increased.
The above references are incorporated by reference herein where appropriate for appropriate teachings of additional or alternative details, features and/or technical background.